Detection method and system for printed circuit board (PCB)

Abstract

The invention discloses a detection method and system for a printed circuit board (PCB), and the method comprises the steps: setting a detection light path which comprises a photoelectric transmitter, a mirror reflection plate and a photoelectric receiver; an included angle is formed between a light emitting path of the photoelectric emitter and a normal line of the specular reflection plate, and a reflection light path of the specular reflection plate coincides with a receiving light path of the photoelectric receiver; controlling a photoelectric emitter to emit detection light; detecting whether the detection light reflected by the mirror reflection plate is received or not through a photoelectric receiver; if the photoelectric receiver does not receive the optical signal, it is judged that a plate exists at the current plate position; and if the photoelectric receiver receives the optical signal, determining that the current plate position has no plate. According to the invention, the detection logic is converted from analog quantity judgment depending on surface reflection characteristics into digital quantity judgment depending on light path shielding, so that the interference of ink color difference and hole structure on the stability of the detection result is fundamentally eliminated.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing and testing technology, and particularly to a testing method and system for printed circuit boards (PCBs). Background Technology

[0002] In the manufacturing process of printed circuit boards (PCBs), especially after the outer layer circuitry and solder mask processes, the detection and precise positioning of components are crucial for ensuring the smooth operation of subsequent processes. Currently, photoelectric sensors based on the principle of diffuse reflection are widely used in this field. Their working principle is as follows: the sensor emits a light beam to the surface of the PCB being measured and receives the light diffusely reflected back from the surface; the internal circuitry of the sensor analyzes the intensity of the received luminous flux and compares it with a preset threshold to determine the presence of the component.

[0003] However, as electronic products develop towards higher density and higher performance, PCB design is becoming increasingly complex, posing a serious challenge to existing diffuse reflection detection methods. The main technical bottlenecks are as follows: Figure 1 As shown in the diagram, this illustrates the optical path failure in diffuse reflection detection when encountering holes. Firstly, modern PCBs typically have numerous through-holes, blind vias, and various irregularly shaped holes. When the light beam emitted by the photoelectric sensor shines on these hole areas or their edges, the light is severely scattered or directly absorbed by the hole walls, resulting in almost no or only a very small amount of light being reflected back to the sensor receiver. This makes the sensor highly susceptible to misjudging a "no board" state, leading to erroneous production line shutdowns or operational errors, impacting production efficiency and yield. Figure 2 As shown in the diagram, the received light flux is unstable when detecting different colored inks using diffuse reflection. Secondly, during the solder mask process, the PCB board surface is coated with inks of different colors (such as green, black, and white) to achieve insulation and protection. These inks have vastly different optical properties; highly reflective bright inks (such as white) reflect most of the incident light, while highly absorbent dark inks (such as black) absorb most of the incident light. The effective detection threshold range of diffuse reflection sensors is limited. When the light flux intensity returned from the surface of different colored boards exceeds or falls below this range, the detection function will fail. In actual production, technicians often need to frequently and manually adjust the sensor sensitivity and installation angle for different colored boards, and may even need to configure different sensors for different production lines. This approach is not only inefficient and increases maintenance costs, but also fails to meet the demands of modern production lines for high efficiency, high flexibility, and mixed production of multiple varieties.

[0004] Therefore, there is an urgent need in the industry to develop a new testing technology that can fundamentally overcome the above-mentioned defects and can stably, accurately, and without frequent adjustments test PCBs with complex hole structures and diverse surface ink colors. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology. To achieve the above objective, a testing method and system for printed circuit boards (PCBs) are provided to solve the problems mentioned in the background art.

[0006] A method for inspecting printed circuit boards (PCBs) includes the following steps: A detection optical path is set up, which includes a photoelectric emitter located on one side of the expected board position, and a mirror reflector and a photoelectric receiver located on the other side of the expected board position; the light output path of the photoelectric emitter forms an angle with the normal of the mirror reflector, and the reflected light path of the mirror reflector coincides with the received light path of the photoelectric receiver. Control the photoelectric emitter to emit detection light; The photoelectric receiver detects whether the detection light reflected by the mirror reflector is received; If the photodetector does not receive a light signal, it is determined that there is a board at the current board position; if the photodetector receives a light signal, it is determined that there is no board at the current board position.

[0007] As a further embodiment of the present invention: the mirror reflector is a plane mirror with high reflectivity, a prism for changing the direction of light path, or a corner reflector with retroreflection characteristics. When the corner reflector is used, the relative positional accuracy requirements of the photoelectric transmitter and the photoelectric receiver are reduced.

[0008] As a further aspect of the present invention: the mounting angle and / or position of the mirror reflector is set to be adjustable to calibrate the reflected light path so that it is precisely aligned with the photodetector.

[0009] As a further aspect of the present invention, the included angle α is in the range of 30° to 60°, so as to ensure effective reflection of the light path while avoiding spatial interference between the photoelectric transmitter and the photoelectric receiver.

[0010] As a further embodiment of the present invention: the photoelectric transmitter and the photoelectric receiver are integrated into a specular reflective photoelectric sensor, the sensor having a protective housing, and the housing having mounting references or visual marks for aligning with the specular reflector.

[0011] As a further aspect of the present invention: all or part of the components in the detection optical path are configured to be movable; By moving the component, the detection optical path can scan a specific area or the entire surface of the PCB board.

[0012] As a further aspect of the present invention: by controlling the detection optical path to scan along a predetermined path, line scanning or area array detection can be achieved; Among them, by analyzing the timing and location of light signal obstruction during the scanning process, the presence or absence of the board can be determined, and the edge contour of the board, the distribution of specific hole areas, or the positioning offset information of the board on the carrier can be obtained.

[0013] As a further aspect of the present invention: the movement process is controlled by a drive mechanism, which is a motor-driven linear module, a rotary mechanism, or a robotic arm; The drive mechanism is connected to the control system, receives position commands and feeds back position information, thereby enabling precise and programmable movement of the detection optical path.

[0014] As a further aspect of the present invention, the detection light is modulated visible or invisible light to enhance the ability to resist ambient light interference.

[0015] The second aspect of the technical solution: A system employing the inspection method for printed circuit boards (PCBs) as described in any of the above claims, comprising: Control unit; The photoelectric transmitter is controlled by the control unit; Mirror reflector; A photoelectric receiver, the output of which is connected to the control unit; The photoelectric transmitter, the mirror reflector, and the photoelectric receiver are arranged according to the optical path relationship described in claim 1. It also includes a drive mechanism connected to the control unit for driving at least one of the photoelectric transmitter, photoelectric receiver and / or mirror reflector to move.

[0016] Compared with the prior art, the present invention has the following technical advantages: The above technical solution employs a specific layout comprising a photoelectric transmitter, a mirror reflector, and a photoelectric receiver: the transmitter and receiver are located on the same side of the intended board location, while the mirror reflector is located on the other side. The transmitter emits light rays at an angle α to the normal of the mirror. After reflection by the mirror, the reflected light path is precisely guided to the receiver. During detection, if there is no PCB board obstructing the light, the light is received by the receiver after reflection by the mirror, indicating "no board"; if a PCB board is present, the light is obstructed, the receiver receives no signal, and the system indicates "board present".

[0017] This technology completely overcomes the sensitivity of traditional diffuse reflection testing to ink color and hole structure on PCB boards. Because the detection logic is based on the physical obstruction (on / off) of the light path, rather than relying on the intensity (strong / weak) of the light signal reflected from the surface of the object being tested, neither highly reflective nor highly absorbent inks will cause false judgments. Simultaneously, holes on the board will not cause signal loss due to light scattering or absorption. This enables stable and reliable testing of PCB boards with complex appearances, and the installation layout is more convenient than through-beam testing. Attached Figure Description

[0018] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings: Figure 1 This is a schematic diagram illustrating the failure of the optical path in diffuse reflection detection when encountering holes in existing technologies. Figure 2 This is a schematic diagram illustrating the instability of received light flux when detecting inks of different colors using diffuse reflection in existing technologies. Figure 3 This is a schematic diagram illustrating the steps of the detection method according to an embodiment of this application; Figure 4 This is a schematic diagram of the installation layout and optical path principle of one embodiment of the system disclosed in this application.

[0019] In the diagram: 1. PCB board; 2. Photoelectric transmitter; 3. Photoelectric receiver; 4. Mirror reflector; 5. Detector light. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 3 In this embodiment of the invention, a method for detecting printed circuit boards (PCBs) includes the following steps: Step S1: Set up the detection optical path. The detection optical path includes a photoelectric emitter located on one side of the expected board position, and a mirror reflector and a photoelectric receiver located on the other side of the expected board position. The light output path of the photoelectric emitter forms an angle with the normal of the mirror reflector, and the reflected light path of the mirror reflector coincides with the received light path of the photoelectric receiver. In this embodiment, the mirror reflector is a plane mirror with high reflectivity, a prism for changing the direction of the light path, or a corner reflector with retroreflection characteristics. When using a corner reflector, the relative positional accuracy requirements for the photoelectric transmitter and the photoelectric receiver are reduced.

[0022] In this embodiment, the mounting angle and / or position of the mirror reflector is set to be adjustable to calibrate the reflected light path so that it is precisely aligned with the photodetector.

[0023] In this embodiment, the included angle α ranges from 30° to 60°, so as to ensure effective reflection of the light path while avoiding spatial interference between the photoelectric transmitter and the photoelectric receiver.

[0024] In this embodiment, the photoelectric transmitter and the photoelectric receiver are integrated into a mirror-reflective photoelectric sensor. The sensor has a protective housing, and the housing is provided with mounting references or visual marks for aligning with the mirror reflector.

[0025] In this embodiment, all or part of the components in the detection optical path are configured to be movable; By moving the component, the detection optical path can scan a specific area or the entire surface of the PCB board.

[0026] In this embodiment, line scanning or area array detection is achieved by controlling the detection optical path to scan along a predetermined path; Among them, by analyzing the timing and location of light signal obstruction during the scanning process, the presence or absence of the board can be determined, and the edge contour of the board, the distribution of specific hole areas, or the positioning offset information of the board on the carrier can be obtained.

[0027] In this embodiment, the movement process is controlled by a drive mechanism, which is a linear module driven by a motor, a rotary mechanism, or a robotic arm. The drive mechanism is connected to the control system, receives position commands and feeds back position information, enabling precise and programmable movement of the detection optical path.

[0028] Step S2: Control the photoelectric emitter to emit detection light; Step S3: Detect whether the detection light reflected by the mirror reflector is received by the photoelectric receiver; Step S4: If the photoelectric receiver does not receive a light signal, it is determined that there is a board at the current board position; if the photoelectric receiver receives a light signal, it is determined that there is no board at the current board position.

[0029] In this embodiment, the detection light is modulated visible or invisible light to enhance the ability to resist ambient light interference.

[0030] The second aspect of the technical solution: A system employing any of the above-mentioned methods for testing printed circuit boards (PCBs), comprising: Control unit; The photoelectric transmitter is controlled by the control unit; Mirror reflector; A photoelectric receiver, the output of which is connected to a control unit; The photoelectric transmitter, the mirror reflector, and the photoelectric receiver are arranged according to the optical path relationship of claim 1; Optionally, it also includes a drive mechanism connected to the control unit for driving at least one of the photoelectric transmitter, photoelectric receiver, and / or mirror reflector to move.

[0031] like Figure 4 As shown, the diagram illustrates the installation layout and optical path principle of one embodiment of the system. The photoelectric transmitter 2 and the photoelectric receiver 3 are integrated into a mirror-reflective photoelectric sensor, which is installed above the intended location of the PCB board 1. A high-precision plane mirror, serving as a mirror reflector 4, is installed below the board's transport track with its mirror surface facing upwards. Its position is precisely calibrated so that the detection light 5 (angle α) emitted by the transmitter 2 is incident on the reflector 4 and reflected by the reflector 4 at a reflection angle β, and is then received by the receiver 3 above.

[0032] During operation, PCB board 1 moves along the transport track to the inspection station. The control system triggers the sensors to perform inspection.

[0033] A (No Board): There are no boards on the transmission track. The detection light 5 shines unobstructed onto the mirror reflector 4 below, and after reflection, all its energy is received by the receiver 3. The receiver 3 outputs a "pass" signal, and the system determines that there is no board at this location.

[0034] B (Board Present): Board 1 is located precisely in the detection optical path. Regardless of the number of holes on its surface or whether it uses bright green or matte black ink, it physically blocks the emitted and / or reflected optical paths. Receiver 3 cannot receive any optical signal and outputs a "disconnect" signal, indicating that the board is present at this location.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A method for inspecting printed circuit boards (PCBs), characterized in that, Includes the following steps: A detection optical path is set up, which includes a photoelectric emitter located on one side of the expected board position, and a mirror reflector and a photoelectric receiver located on the other side of the expected board position; the light output path of the photoelectric emitter forms an angle with the normal of the mirror reflector, and the reflected light path of the mirror reflector coincides with the received light path of the photoelectric receiver. Control the photoelectric emitter to emit detection light; The photodetector detects whether the detection light reflected by the mirror reflector is received. If the photodetector does not receive a light signal, it is determined that there is a board at the current board position; if the photodetector receives a light signal, it is determined that there is no board at the current board position.

2. The method for testing printed circuit boards (PCBs) according to claim 1, characterized in that, The mirror reflector is a plane mirror with high reflectivity, a prism for changing the direction of light path, or a corner reflector with retroreflection characteristics. When the corner reflector is used, the relative positional accuracy requirements of the photoelectric transmitter and the photoelectric receiver are reduced.

3. The method for testing printed circuit boards (PCBs) according to claim 2, characterized in that, The mounting angle and / or position of the mirror reflector is set to be adjustable to calibrate the reflected light path so that it is precisely aligned with the photodetector.

4. The method for testing printed circuit boards (PCBs) according to claim 1, characterized in that, The included angle α ranges from 30° to 60° to ensure effective reflection of the light path while avoiding spatial interference between the photoelectric transmitter and the photoelectric receiver.

5. The method for testing printed circuit boards (PCBs) according to claim 1, characterized in that, The photoelectric transmitter and the photoelectric receiver are integrated into a specular reflective photoelectric sensor. The sensor has a protective housing, and the housing is provided with mounting references or visual marks for aligning with the specular reflector.

6. The method for testing printed circuit boards (PCBs) according to claim 1, characterized in that, All or some of the components in the detection optical path are configured to be movable; By moving the component, the detection optical path can scan a specific area or the entire surface of the PCB board.

7. The method for testing printed circuit boards (PCBs) according to claim 6, characterized in that, By controlling the detection optical path to scan along a predetermined path, line scanning or area array detection can be achieved; Among them, by analyzing the timing and location of light signal obstruction during the scanning process, the presence or absence of the board can be determined, and the edge contour of the board, the distribution of specific hole areas, or the positioning offset information of the board on the carrier can be obtained.

8. The method for testing printed circuit boards (PCBs) according to claim 7, characterized in that, The movement process is controlled by a drive mechanism, which is a motor-driven linear module, a rotary mechanism, or a robotic arm. The drive mechanism is connected to the control system, receives position commands and feeds back position information, thereby enabling precise and programmable movement of the detection optical path.

9. The method for testing printed circuit boards (PCBs) according to claim 1, characterized in that, The detection light is modulated visible or invisible light to enhance its resistance to ambient light interference.

10. A system employing the inspection method for printed circuit boards (PCBs) as described in any one of claims 1 to 9, characterized in that, include: Control unit; The photoelectric transmitter is controlled by the control unit; Mirror reflector; A photoelectric receiver, the output of which is connected to the control unit; The photoelectric transmitter, the mirror reflector, and the photoelectric receiver are arranged according to the optical path relationship described in claim 1. It also includes a drive mechanism connected to the control unit for driving at least one of the photoelectric transmitter, photoelectric receiver and / or mirror reflector to move.

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